Separation of organic acids from alcohols



Jan. 1, 1952 HYDROCARBON RECYCLE w. P. BURToNl-:r A1.

SEPARATION OF ORGANIC ACIDS FROM ALCOHOLS Filed April 50, 1947 ACIDS AND ALGOHOLS WILLIAM P. BURTON HENRY G.M*GRATH Lou C. RUBIN BYggT.

ATTORNEYS Patented Jan. l, 1952 SEPARATION OF ORGANIC ACIDS FROM ALCOHOLSl William P. Burton, Orange, Henry G. McGrath, Elizabeth, and Louis C. Rubin, West Caldwell, N. J., assignors to lThe M. W. Kellogg Company, Jersey City, N. J., a corporation of Dela- Ware Application April 30, 1947, Serial No. 745,004

13 Claims. (Cl. 26o-450) This invention relates to the separation of organic compounds. In one of its more specific aspects, the invention relates to the separation of oxygenated organic compounds from the reaction product obtained in the reduction of oxides of carbon with hydrogen in the presence of a catalyst. More particularly, this invention is directed to an improved process for the separation of organic acids, alcohols, and other oxygenated organic compounds present in the reactor gases obtained from the aforementioned catalytic hydrogenation of oxides of carbon at elevated temperatures.

In the hydrogenation of oxides of carbon in the presence of a reducible metal catalyst at elevated temperatures, a reactionproduct is obtained in the form of reactor outlet gases at temperatures falling between about 300 F. to about 700 F., and containing oxygenated organic compounds comprising acids, alcohols, aldehydes, ketones and esters. These gases are passed through one or more condensation zones in which they are cooled to temperatures Within the range from about 40 F. to about 150 F. to eect separation of the resulting condensate into a Water-rich phase and an oil phase. Both phases contain oxygenated organic compounds, those of lower molecular Weight tending to remain in the Water phase, While those of higher molecular weight tend to remain in the oil or non-aqueous liquid phase.

At one stage in the process for the recovery of oxygenated organic compounds from the aforementioned oil or non-aqueous liquid phases, there is obtained a mixture of alcohols and organic acids, both Water-insoluble, and containing relatively smaller quantities of other water-insoluble oxygenated organic compounds, comprising aldehydes, ketones and esters. It has been found that these organic acids may be separated from mixtures thereof With one or more of the aforemenwhen strong caustic solutions (5% or greater) are employed it is diflicult to separate the resulting salts of the fatty organic acids from alcohols and other oxygenated organic compounds, by reason of the hydrotropic effect of the salts thus formed. Furthermore, we have found that this hydrotropic effect is increased with increased concentrations of alkali employed. On the other hand, when sufficiently dilute alkali is employed to obtain efficient separation of the salts from the aforementioned oxygenated organic compounds, the presence of increased quantities of water thus introduced, makes subsequent acid recovery undesirable from an economic standpoint.

The present invention, therefore, is directed to a process, as more fully hereinafter described, for separating Water-insoluble organic acids from mixtures thereof with Water-insoluble alcohols, or from such mixtures which contain in addition, other water-insoluble oxygenated organic compounds comprising aldehydes, ketones and esters. In general, the process comprises, broadly, the steps of neutralizing such mixtures with a strong alkaline solution to convert the organic acids contained therein to their corresponding organic salts, diluting the alkali to obtain desired concentrations and effecting separation of these salts from other oxygenated organic compounds by extracting the latter with a water-insoluble liquid organic or inorganic solvent.

We have found that such Water-insoluble liquid solvents may be used as sulfur dioxide, halogenated compounds, ethers, esters and other waterinsoluble liquid oxygenated organic compounds such as ethyl acetate, di-ethyl ketone and methyl butyl ketone.

In addition, We have found that overall generally satisfactory results have been obtained by employing, as a solvent, a hydrocarbon or a mixture of hydrocarbons, and preferably such a hydrocarbon or mixture of hydrocarbons, which does not form a minimum boiling azeotrope with oxygenated organic compounds in the aforementioned extract phase.

The insolubility of the solvent in the aqueous salt solution and its mutual solubility with the layer of oxygenated organic compounds, causes the phase separation to take place. The solvent is subsequently removed from both the layer of oxygenated compounds and the aqueous salt layer by distillation and recycled to the extraction step for reuse. The solvent-free aqueous salt layer is subsequently acidied with an inorganic acid, and the mixture thus obtained is separated into an acidrich phase, comprising substantially Water-insolu- Vble organic acids, and av water-rich phase which comprises substantially inorganic salts and any Water-soluble organic acids that may be present. Particular advantage is obtained. as more fully hereinafter described, in that the aforementioned steps of neutralization, extraction and alkali dilution are carried out within a single piece of equipment.

It is therefore an object of the present invention to provide an improved process for separating water-insoluble organic vacids from mixtures thereoi with other water-.insoluble oxygenn ated organic compounds.

Another objectY of the invention is to provide an improved process for separating water-in-f soluble organic acids from mixtures thereof with Water-insoluble alcohols.

Still another object of the invention is to provide an improved process for separatimgl water insoluble organic acids from mixtures thereof with water-insoluble alcohols, aldfhydes, ketones and esters,

Other objects and advantages inherent in the invention will be apparent from the following more detailed disclosure.

The accompanying drawing illustrates, diagrammatically, one iorrrijV of the apparatus emrloyed and @arablev cigarrillos out one embodiment or the process o this invention. While 'the` inventionA will be described in detail by ref erence to one embodimenthof the processy ernploying the apparatusV illustrated in the draw,-l ing, it'should be noted that it is not intended that the invention be limited to the embodiment as illustrated, but is capable of other embodiments beyond the scope of the` apparatus illustrated in the drawing. Pumps, compressors, valves and other mechanical elements necessary to effect the transfer of liquids and vapors and to maintain the conditions of temperature and pressure necessary to carry out the function of the apparatus, are omitted to simplify the description, much equipment of this nature is necessary and will be supplied by those skilled in the art.

Referring to the drawing, a mixture of waterinsoluble organic acids and alcohols is supplied through line IQ. This mixture may contain in addition, other oxygenated organic compounds comprising aldehydes, ketones and esters, in whole or in part, This mixture transferred through line I to a point near the center of a caustic treater Il. introduced through line I is treated with alkali by countercurrent contact to neutralize the aforementioned organic acids. Alkali thus employed, converts organic acids contained in the aforementioned acid-alcoholl mixture to their corresponding Organi@ Salts For this, purpose, the mixture thus introducedv into treater Il iS intimately mixed with any aqueous alkali'in a suitable amount, introduced into treater II at an upper point through line I2; 1n accordance with the process of the invention, such aqueous alkaline solution may comprise a strongsolution having a concentration ofl alkali in the amount of 5% or greater, In this respect, it has been found that caustic solutions in concentrations of approximately to 50% have proved overall satisfactory, in converting organic acids to their salts from acid-alcohol mixtures, as derived from the reaction product obtained in theV aforementioned catalytic hydrogenation or" oxides of oar bon at elevated temperatures.`

To facilitate separation ofY excess alkali and organic salts from the neutralized alcohols and any of the aforementioned oxygenated organic compounds that may have been present in the feed introduced through line I0, the mixture of organic salts, oxygenated organic compounds and excess alkali, is next contactedwith water. introduced into treater II at an upper point above the introduction of the alkali, through line I3. The quantity of water thus utilized is limited to the minimum necessary to,v effect asuitable sepa-ra.u tion of organic salts and excess alkali from al- 1t will be understood, however, that In treater II the mixture 0011015. and Qther Oxygena'tad organic. Compounds or to dilute the alkali to any desired concentra tion.

In order to effect complete separation of alcohols and other oxygenated organic compounds from organicv salts aqueous solution in treater II., a light hydrocarbon stream, employed as the solvent treating agent in the instant embodiment of our invention, is introduced at a point near the bottom of treater II through line I4. This solvent treating agent comprises a hydrocarbon or a mixture of hydrocarbons, or a hydrocarbon or mixture of hydrocarbons which preferably does not form a minimum boiling azeotrope with the aforementioned alcohols and other oxygenated organic compounds present. W e have found such hydrocarbons as butane, pentane or hexane, either individually or in'mixtures thereof', to ne overall generally suitable as the solvent treating agent as applied to the present process. The admixture of the introduced hydrocarbon stream with salts of organic acids present, tends to con fine these salts in the lower aqueous layer which is formed in treater Il. At this point, it will be noted that the introduction of the aforemen- Y tioned hydrocarbon stream into treater AII through line I4 as described above, make possible the use of strong caustic solutions for the purpose indicated, Without increasing the quantity of Water otherwise required to dilute the caustic in order to obtain efficient separation oi organic salts from the aforementioned oxygenated ore ganic compounds. Treat-er l! may be ordinarily operated at room temperature and at atmos pheric pressure. However, it may be desirable to operate at a temperature above or below an bient temperature in order to maintain maxi mum selectivity of the solvent treating agent. In addition, it may be desirable to operate treater II above atmospheric pressure, as when propane is used as the solvent, in order to maintain the solvent in the most selective condition.

As a result of the treatment of the water-insoluble oxygenated organic chemical mixture, introduced into Vtreater I I through line IE, a phase separation takes place by reason of the insolubilityof the hydrocarbon solvent treating agent in the aqueous salt solution and its mutual solu-V bility with thelayer of oxygenated organic compounds. Accordingly, there is present in treater II an upper hydrocarbon or oil layer comprising proportionately large quantities of the hydrocarbon solventtreating agent, alcohols and other oxygenatedV organic compounds, which as previously described', may comprise aldehydes, ke tones and esters. This upper layer is withdrawn as an extract from treater II through line I5. The lower layer in treater il, comprises an aqueous mixture of'salts of vorganic acids, proportionately smallV quantities of the hydrocarbon solvent treating agent and excess alkali, and` is withdrawn as bottoms through line 5 Vfor further use or treatment in the process hereinafter described.

The extract or oilv layer from treater II, containingv theV solvent treating agent, alcohols and other oxygenated organic compounds is transferred through line I5 to a distillation tower I'I. rIl'ower I'I is operated under conditions effective to separate the aforementioned extract introduced .through .line I5, into an upper fraction comprising substantially vaporized hydrocarbons, and a lower fractionV comprisingI acid-free alcohols and other oxygenated organic compounds. The va:- porized hydrocarbons in tower I'I are withdrawn W wir uw of individual components, where so desired.

As described above, the lower layer in treater II, comprising an aqueous mixture ofsalts of organic acids, proportionately small quantities of the hydrocarbon solvent treating agent and excess alkali is withdrawn as bottoms through line I6. .This mixture is next transferred through line I6 to a distillation tower 23. In tower 23, the mixture is heated under proper operating conditions of temperature and pressure effective to distill overhead the solvent treating agent, which is withdrawn through line 24 and is recycled via line I4, with which line 23 connects, and is thus transferred for reuse in treater I I, in the process hereinbefore described. Bottoms from tower 23, comprising an aqueous mixture of salts of organic acids and excess alkali, are withdrawn through line 25.

Bottoms from tower 23 comprising an aqueous mixture of salts of organic acids and excess alkali, as described above, are transferred through line 25 to a mixer 28. Mixer 2S is provided to intimately mix the mixture introduced through line 25., with an inorganic acid which is introduced into line 25 through line 29, in order to effect complete regeneration of the organic acids from the salts. The inorganic acid thus introduced into mixer 28, may be a high boiling inorganic acid having a boiling point higher than that of Water, such as sulfuric acid, or an inorganic acid which forms a maximum boiling azeotrope with water, such as hydrochloric acid.

The resulting aqueous mixture from mixer 28,V

comprises free organic acids and alkali salts of the introduced inorganic acid. This mixture is withdrawn from mixer 28, through line 3D, and transferred to a separator 3|. In separator 3I heavier organic acids will separate from the water solution .by reason of their insolubility. These acids, comprising an upper acid-rich phase in separator 3|, are withdrawn overhead through line 32 for further treatment outside the scope ofthe present process, to obtain separatii of individual acids where so desired.

The lower water-rich phase in separator 3l, comprising inorganic salts, any excess quantities of the introduced inorganic acid and light organic acids, is withdrawn as bottoms from separator 3I through line 33. This lower water-rich phase is next transferred through line 33 to a low point in a distillation tower 34, which functions as an acid stripper. Tower 34 is heated under conditions effective to distill overhead the light organic acids as their water azeotropes which are withdrawn through line 35, and may be subjected to further treatment, outside the scope of the present process, to obtain separation of individual acids Where so desired. Bottoms from tower 34. comprising inorganic salts, excess quantities of the introduced inorganic acid and water are Withdrawn through line 3B for further use or treatment. outside thescope of the present process. It should be noted that where so desired separation of organic acids in line 33 may be .organic compounds.

effected by extraction processes known to those skilled in the art, instead of by distillation, as described above.

As an example of the efficacy of the aforementioned process, as demonstrated by laboratory operations in accordance with the above described procedure, a mixture of water-insoluble alcohols, aldehydes, ketones, esters, and organic acids, containing 35 weight percent of a mixture of organic acids having a molecular weight equivalent to the molecular weight of heptanoic acid, was neutralized with a 15% sodium `hydroxide solution. It was observed upon the admixture of the acids` with the caustic, that no phase separation was obtained between acids, as

their organic salts, and remaining oxygenated However, upon the addition of `pentane,..in the ratio of one volume pentane per. volume of the aforementioned acid-oxy- 'thereof with water-insoluble alcohols and other oxygenated organic compounds, present in the oil or non-aqueous liquid product obtained from the condensation of reactor gases in the catalytic hydrogenation of oxides of carbon at elevated temperatures. However, while the invention has been described as having a particular applicability to the separation of such compounds obtained from the source indicated, it should be noted that the process of the invention is not necessarily restricted to effect the desired separation of these compounds as derived from the aforementioned source. The process of the invention may be also successfully applied to the separation of any mixtures of the aforementioned compounds, without regard to the source from which these mixtures may have been derived and without regard to the relative proportions of the components comprising such mixtures. It should be also noted that while we have shown the aforementioned steps of neutralization, extraction and alkali dilution as being carried out in a single piece of equipment as exemplied by treater II, the aforementioned steps can be also successfully carried out in separate pieces of equipment, each respectively designed to carry out the aforementioned functions.

In addition, while we have described. a particular embodiment of our invention for purposes of illustration, it should be understood that various modications and adaptations thereof, which will be obvious to one skilled in the art, may be made within the spirit of the invention as set forth in the appended claims.

Having thus described our invention, what we claim and desire to secure by Letters Patent is:

1. A process for separating organic acids and alcohols from a mixture thereof, which comprises: introducing a water-insoluble solvent into the lower portion of a reaction zone; introducing an aqueous solution of an alkali into the upper portion of said zone; introducing the mixture of said acids and alcohols into said zone at a point between vthe points of 4introduction of said water-insoluble solvent and said aqueous alkali solution to form an extract phase comprising alcohols and a raffinate phase comprising alkali salts; and separating said phases.

2. A process as dened in claim 1 wherein said 7 solvent is a liquid oxygenated organic compound.

3. A process as defined in claim 1 wherein said solvent is ethyl acetate. v

ll. A. process as donned in claim l wherein said solvent isa liquid hydrocarbon.

5. A process as. oeined in claim 1 wherein .said solvent is a liquid hydrocarbon which does` not form a minimum boiling` azeotrope. with. said alcohols.

6. A process as defined in claim 1 whereinsaid solvent is pentane.

'1. A process llor separating organic acids, and alcohols from a mixture. thereof., which com,- prises: introducing a water-insoluble solventiinfto the lower portion of a reaction zone.; .introducing an allali'into the upper portion. of said zone.; introducing water into said zone at av point; above the point of introduction .of said alkali; intro.- ducing the mixture of' said acids and. alcohols into said zone at a point between the points. of introduction oi said water-insoluble solvent and said alkali to form an extract phase comprising alcohols and a raflinate phase comprising alkali salts; and separating said phases.

S. A process for seprating organic acids and alcohols iron-1 a mixture thereof, which comprises: introducing a water-insolublesolvent into the lower portion of a reaction zone; introducing an aqueous solution of .an alkaliA into4 the upper portion or said zone.; introducing the mixture of said acids and alcohols into said zone at-a1.point betweenv the points or introduction of' said waterinsoluble solvent and said aqueousalkali solution to form: extract fphase.comprisingalcoholsand solvent and ay raiiinate phase. comprising alkali salts; separating said phases; recoveringf solvent from said extract phase; and passing solvent thus recovered .to said first-mentioned treatment of said. mixture of organic. acids and alcohols to supply at least a portionv of. the. solvent to said treatment.

.9. A process for separating organiczacids and alcohols from a mixture thereof', whichcomprises: introducing a waterfinsoluble solvent into the lower portion of a reaction zone; introducing an aqueous solution. of an alkali into the upper portion. ol' said zone; introducing the mixture of said acids and. alcohols into said Zone at a point between the pointsof introduction of saidwater.- insoluble. solvent and said aqueous alkali solution to form an extract phase comprisingr alcohols and solvent. and a. raffinate, phase comprising all-:ali salts and solvent; separating said phases; recovering solvent from each of said phases; and passing vsolvent thus. recovered to4 said. first: mentioned treatment of said mixture of organic` acids and alcohols to supply atleast a portion of the solvent to said treatment.

lll. A process for separating organic acids and alcohols from a mixture thereof obtained in a process for the catahftic hydrogenation of an oxide of carbon, which comprises: introducing a waterfinsoluble. solvent into thelower portion of a reaction zone; introducing an. aqueous solution of an alkali into the upper portion of said Zone; introducing Vthe mixture of said acids. and alcohols into said zone at; a point. between. the points of introduction of said water-.insoluble solvent and said aqueous alkali. solution to.' form an extract phase comprising alcohols. and a raiinate phase. comprising: alkali. salts; andy separatingasaidphasesa.

11. A. process for separating organcacidsand 8. lalcol-101s :from a mixture thereotobtalnedrln' a process forl the catalytic hydrogenation of.; an ox ide of carbon,. which comprises:v introducing- .a

water -insoluble solvent into the lower portionotia reaction zone.; introducing an alkali into the upper portion of said. zone; introducingwater into said zone at a point above the point of: introduc tionof said alkali; introducing.V themvxturel off said acidsv and alcohols. into said. zone at a. point be' tween the. points of introduction of. saidwater- .insoluble solvent. and said alkali to form an exoxide. of carbon, which. comprises: introducingY a'. water-.insoluble solvent into the lower portion of. a.- reaction zone.; introducing airaqueous soluz-V tion of an. alkali into. the upper portion off. said zone; introducing. the mixture. of` said: acids and alcohols. into saidv zone at. a. point. between the points` of introduction of said watereinsoluble y solvent and said aqueous alkali. solution to form an extract. phase comprising alcohols and sol-vent and a. rafinate phase. comprising .alkali salts; separating said phases; recovering solvent from said extract phase; and passing solvent thussrefcovered to said first-mentioned treatment olif said mixture of organic acids and alcohols; tol supply at least a. portion of the solvent to said treat@ ment.

13 A process for separating organic; acids and alcoholsrr from a mixture thereof obtained inea process for the catalytic hydrogenation off. an oxide of carbon, whichv comprises:v introducing a. water-insoluble solvent into the lower portion of a. reaction'. zone; introducing an aqueous: soluztion. of an alkali into the upper portion of said zone;y introducing the mixture of saidY acids; and alcohols: into said zone at a point between the points of introductionv of said water-,insoluble solvent and said aqueous. alkaliy solution to-form an extract phase comprising alcohols and solvent and a rafl'inate phase comprising alkaliy salts and solvent; separatingl said phases; recovering sol.- vent from each of said. phases; and passing. sol, vent thus recovered toi said first-mentioned treatsment of. said mixture. of organic acids and alec;- hols` to supply at least a.- portionk ofA the. solvent to said treatment.

WILLIAM' P. BURTON; HENRY G. MCGRATH.. LOUIS C. RUBIN.`

EEFERENGESf The followingv references are of? record' inv the llle ofy this patent:

OTHER REFERENCES Koch eti al.,.Brenn..Chem.` 16, 382-387` (193535. 

1. A PROCESS FOR SEPARATING ORGANIC ACIDS AND ALCOHOLS FROM A MIXTURE THEREOF, WHICH COMPRISES: INTRODUCING A WATER-INSOLUBLE SOLVENT IN TO THE LOWER PORTION OF A REACTION ZONE; INTRODUCING AN AQUEOUS SOLUTION OF AN ALKALI INTO THE UPPER PORTION OF SAID ZONE; INTRODUCING THE MIXTURE OF SAID ACIDS AND ALCOHOLS INTO SAID ZONE AT A POINT BETWEEN THE POINTS OF INTRODUCTION OF SAID WATER-INSOLUBLE SOLVENT AND SAID AQUEOUS ALKALI SOLUTION TO FORM AN EXTRACT PHSE COMPRISING ALCOHOLS AND A RAFFINATE PHASE COMPRISING ALKALI SALTS; AND SEPARATING SAID PHASES. 